1. Field of the Invention
This invention relates to continuous passive motion apparatus for mobilizing the knee joint of the patient's leg.
2. Description of the Prior Art
In recent years, there has been an increasing awareness of the advantages of mobilization of joints as a part of the orthopedic care which follows an injury, an illness, or a surgical procedure. A joint can stiffen rapidly as a result of immobilization, and in many cases extensive therapy is required in order to regain full use of the joint after it has stiffened.
Active motion of a joint occurs when the patient has sufficient muscle strength to flex or extend the limb without need for external applied force. In contrast, passive motion of a joint involves the use of an external force to flex and extend the limb to induce motion. Continuous passive motion of a joint following injury, illness or surgery has been found to reduce post-operative pain, decrease adhesions, decrease muscle atrophy, and enhance the speed of recovery, while minimizing other risks of immobilization such as venous stasis, thromboembolism and post-traumatic osteopenia.
Continuous passive motion (CPM) devices developed in the past have, in general, included a base or frame, a femur support which supports the upper part of the leg, a tibia support which supports the lower part of the leg, and a drive system. The femur support typically is pivoted with respect to the base while while the tibia support pivots with respect to the femur support and is supported above the frame. Examples of this type of device are shown in the Ragon et al U.S. Pat. No. 3,450,132, the Bimler U.S. Pat. No. 3,717,144 and the Pecheux U.S. Pat. No. 4,323,060.